1,800 feet (545 m.) above sea level, but is not a uniform 

 plain. Several deep valleys traverse it, one of which was 

 incised by the water of the South Saskatchewan river, at 

 a time when the northward flow of that stream was blocked 

 by glacial ice. This channel is now occupied by a small 

 stream called Qu'Appelle river. Streams flowing eastward 

 across the plateau have cut deep valleys into the escarp- 

 ment which rises from the lower prairie level to the east 

 and have left remnants standing as isolated hills which 

 are known as the Pembina, Riding, Duck, and Porcupine 

 mountains. 



The drainage is eastward into a confluent series of 

 streams entering the Assiniboine valley and northeastward 

 into the Saskatchewan. Wooded areas occur in the north 

 and along the outer edge of the plateau, while a few of 

 the higher levels of the central surface are similarly covered. 



Third Division. — This area, extending from the 

 Coteau, or the hilly country just west of Moosejaw, to 

 the foothills of the Rockies, is divided by the depression 

 through which the South Saskatchewan river flows. To 

 the north of this depression the drainage is mainly eastward 

 to the North Saskatchewan, while the region to the south 

 includes a fringe of the drainage basin of the Missouri 

 river. There is also immediately west of the Coteau a 

 small basin without outlet whose waters evaporate in 

 Lakes Johnston and Chaplin. 



The relief in this division is accentuated by the fact 

 that much of it is bare of trees, so that such elevations as 

 the flat topped Cypress Hills standing 2,000 feet (608 m.) 

 above the railway near Medicine Hat or the Hand Hills 

 800 feet (243 m.) above the surrounding plains, become 

 prominent topographical features. 



Fourth Division. — The topographic character of the 

 foothills is much more diverse than that of the other 

 divisions. The geological structure is closely related to 

 the topography, and all the hills are formed of folded or 

 faulted rock masses. 



Since the folding in these hills is due to the same 

 causes that produced the Rocky mountains, the strike of 

 the folds follow directions nearly parallel to the mountain 

 chain. Although often of considerable elevation the 

 summits of the foothills are not as serrated as the moun- 

 tains, since the rocks composing them are of softer mater- 

 ials. Their flanks also are either grassed or clothed with 



